Current automotive vehicles include passive inflation devices, commonly known as xe2x80x9cairbagsxe2x80x9d, which inflate during a collision to impede the forward momentum of a vehicle passenger. Each airbag is stored in a deflated state within a compartment behind the vehicle instrument panel. An inflation device, currently based on pyrotechnic gas generation, is activated by a collision sensor to generate the gas used to inflate the airbag. The expansion force created by the gas generation propels the airbag through a pre-weakened panel formed in the instrument panel.
The pre-weakened panel typically includes a pre-weakened edge and a non-weakened side used as a pivot point for the entire panel. The instrument panel skin, typically formed of vinyl plastic is pre-weakened, typically by scoring from the backside. Laser scoring apparatus have been employed to form a slot or a series of spaced apertures in the backside of the instrument panel skin to a predetermined depth to form the pre-weakened seamless panel edge.
It is imperative for appearance as well as proper timed deployment of the airbag during a collision, that the scored slot be of a constant and appropriate depth along the entire pre-weakened edge of the panel. If the slot is too deep, the slot may be visible from the exterior side of the instrument panel. At the same time, any force exerted on the panel from the exterior side of the instrument panel could break the remaining portion of the scored edge.
Alternately, if the scored slot is too shallow, there may not be sufficient force generated by the airbag during deployment to break through the pre-weakened edge along the entire extent of the pre-weakened edge. This could interfere with the proper timed full deployment of the airbag.
In order to insure the constant and appropriate depth slot, various measurement techniques have been employed, including laser triangulation, ultrasonic measurement, and light transmission through remaining material at the score slot.
While all of these measurement techniques have advantages and disadvantages, the disadvantages are amplified when it is desirable to mount the typically thin outer skin of the instrument panel on one or more backing layers and a rigid substrate. The pre-weakened edge must be formed through all of the substrate and backing layers and into the predetermined depth in the instrument panel skin. Measurement of the slot or hole depth when a backing and/or substrate is employed is much more difficult due to the depth of the slot or hole which blocks a portion of the light to and from the sensor making it difficult to accurately measure the exact depth of the slot or hole. In the light transmission method, the remaining thickness of material in the instrument panel skin must be thin enough to let enough light pass through for measurement. Sometimes the remaining thickness is thinner than desired. In addition, the light transmission method is dependent upon the optical properties of the material. When the manufacture changes material, it must recalibrate the measurement process and adjust the scoring process thereby increasing cost and production downtime. The ultrasound measurement method lacks measurement precision.
Thus, it would be desirable to provide a measurement apparatus and method used with a laser scoring process to accurately measure the depth of the score slot or holes despite any additional backing layers and substrates mounted on the outer skin. It would also be desirable to provide a slot measurement apparatus and method which provides accurate slot depth measurement despite any exterior surface irregularities in the outer layer or skin.
The present invention is an apparatus and method for forming a slot of a predetermined configuration in an article, with the remaining depth between the bottom of the slot and the opposed surface of the article held constant along the entirety of the slot despite any surface dimensional variations in the article.
In one aspect, the present inventive method includes the steps of:
generating a scoring light beam;
using the scoring light beam to form a slot in the article of a predetermined depth in the first surface; and
confocally determining the remaining thickness in the article between a bottom of the slot and the opposed second surface of the article.
In another aspect of the invention, the inventive apparatus includes a source for directing a scoring laser beam onto a first surface of an article to form a slot in the article, and means for confocally sensing the remaining thickness in the article between a bottom of the slot formed by the beam and the other of the first and second surfaces of the article.
The apparatus and method of the present invention uniquely and efficiently provides a constant remaining thickness in an article between the bottom of a scored slot in the opposed surface of the article along the entirety of the slot despite any dimensional surface variations in the article. The confocal slot depth detection of the present apparatus and method enables the depth of the slot to be determined in real time to accurately control the application of a scoring laser beam during formation of each point along the entirety of the slot.